/* ============================================
   SIDEBAR
   ============================================ */
.sidebar-header {
  padding: var(--space-5) var(--space-4);
  border-bottom: 1px solid var(--border-primary);
}

.sidebar-progress-summary {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.sidebar-progress-label {
  font-size: var(--text-xs);
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: var(--weight-medium);
}

.sidebar-progress-value {
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  color: var(--text-primary);
}

.sidebar-nav {
  padding: var(--space-3) 0;
}

.sidebar-module {
  border-bottom: 1px solid var(--border-primary);
}

.sidebar-module:last-child {
  border-bottom: none;
}

.sidebar-module-header {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-3) var(--space-4);
  text-align: left;
  transition: background var(--transition-fast);
}

.sidebar-module-header:hover {
  background: var(--bg-tertiary);
}

.sidebar-module-left {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.sidebar-module-number {
  display: block;
  font-size: var(--text-xs);
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: var(--weight-medium);
}

.sidebar-module-title {
  display: block;
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  color: var(--text-primary);
}

.sidebar-chevron {
  color: var(--text-tertiary);
  transition: transform var(--transition-fast);
  flex-shrink: 0;
}

.sidebar-module.expanded .sidebar-chevron {
  transform: rotate(90deg);
}

.sidebar-topics {
  padding: 0 var(--space-4) var(--space-3);
}

.sidebar-topic {
  display: flex;
  align-items: flex-start;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--text-secondary);
  transition: all var(--transition-fast);
  margin-left: var(--space-6);
}

.sidebar-topic:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.sidebar-topic.active {
  background: var(--pink);
  color: white;
}

[data-theme="dark"] .sidebar-topic.active {
  background: var(--pink-dark);
}

.sidebar-topic.completed .sidebar-topic-indicator svg {
  color: var(--color-success);
}

.sidebar-topic-indicator {
  flex-shrink: 0;
  width: 16px;
  height: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-top: 2px;
}

.sidebar-topic-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--border-secondary);
}

.sidebar-topic.active .sidebar-topic-dot {
  background: white;
}

.sidebar-topic-title {
  line-height: var(--leading-tight);
}

/* ============================================
   DASHBOARD
   ============================================ */
.dashboard {
  max-width: 900px;
}

.dashboard-hero {
  text-align: center;
  padding: var(--space-12) 0 var(--space-8);
}

.dashboard-eyebrow {
  display: inline-flex;
  align-items: center;
  background: var(--yellow);
  color: var(--ink);
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  padding: 4px 12px;
  border-radius: var(--r-full);
  letter-spacing: 0.03em;
  text-transform: uppercase;
  margin-bottom: var(--space-3);
}

.dashboard-title {
  font-size: var(--text-4xl);
  font-weight: var(--weight-extrabold);
  letter-spacing: -0.02em;
  margin-bottom: var(--space-2);
}

.dashboard-subtitle {
  font-size: var(--text-lg);
  color: var(--text-secondary);
  margin-bottom: var(--space-8);
}

.dashboard-stats {
  display: flex;
  justify-content: center;
  gap: var(--space-8);
}

.dashboard-stat {
  display: flex;
  flex-direction: column;
  align-items: center;
}

.dashboard-stat-value {
  font-size: var(--text-3xl);
  font-weight: var(--weight-extrabold);
  color: var(--pink);
}

[data-theme="dark"] .dashboard-stat-value {
  color: var(--pink-light);
}

.dashboard-stat-label {
  font-size: var(--text-sm);
  color: var(--text-tertiary);
}

.dashboard-section-title {
  font-size: var(--text-xl);
  font-weight: var(--weight-semibold);
  margin-bottom: var(--space-5);
}

.module-cards {
  display: grid;
  gap: var(--space-4);
}

.module-card {
  display: block;
  padding: var(--space-6);
  background: var(--bg-elevated);
  border: 1px solid var(--border-primary);
  border-radius: var(--r-xl);
  box-shadow: var(--shadow-xs);
  transition: all var(--transition-fast);
  text-decoration: none;
  color: inherit;
}

.module-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  border-color: var(--border-secondary);
  color: inherit;
}

.module-card-header {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-3);
}

.module-card-icon {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: color-mix(in srgb, var(--module-color) 12%, transparent);
  border-radius: var(--r-full);
  color: var(--module-color);
  flex-shrink: 0;
}

.module-card-number {
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.module-card-title {
  font-size: var(--text-lg);
  font-weight: var(--weight-semibold);
  margin-bottom: var(--space-2);
}

.module-card-desc {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  line-height: var(--leading-relaxed);
  margin-bottom: var(--space-4);
}

.module-card-footer {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.module-card-progress-bar {
  flex: 1;
  height: 4px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.module-card-progress-fill {
  height: 100%;
  background: var(--module-color);
  border-radius: var(--radius-full);
  transition: width var(--transition-slow);
}

.module-card-progress-text {
  font-size: var(--text-xs);
  color: var(--text-tertiary);
  white-space: nowrap;
}

.dashboard-cta {
  text-align: center;
  padding: var(--space-8) 0;
}

.dashboard-cta-text {
  color: var(--text-secondary);
  font-size: var(--text-sm);
  max-width: 500px;
  margin: 0 auto;
}

/* ============================================
   TOPIC VIEW
   ============================================ */
.topic-view {
  padding-bottom: var(--space-12);
}

.topic-breadcrumb {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--text-tertiary);
  margin-bottom: var(--space-6);
  flex-wrap: wrap;
}

.topic-breadcrumb a {
  color: var(--text-tertiary);
}

.topic-breadcrumb a:hover {
  color: var(--text-primary);
}

.topic-header {
  margin-bottom: var(--space-8);
}

.topic-header-meta {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-3);
}

.topic-module-badge {
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
}

.topic-time {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  font-size: var(--text-xs);
  color: var(--text-tertiary);
}

.topic-title {
  font-size: var(--text-3xl);
  font-weight: var(--weight-bold);
  letter-spacing: -0.02em;
  line-height: var(--leading-tight);
}

.topic-sections {
  display: flex;
  flex-direction: column;
  gap: var(--space-6);
}

/* ============================================
   CONCEPT SECTIONS (ACCORDION)
   ============================================ */
.concept-section {
  background: var(--bg-elevated);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.concept-section.expandable .concept-header {
  cursor: pointer;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-5) var(--space-6);
  text-align: left;
  transition: background var(--transition-fast);
}

.concept-section.expandable .concept-header:hover {
  background: var(--bg-secondary);
}

.concept-section:not(.expandable) {
  padding: var(--space-5) var(--space-6);
}

.concept-title {
  font-size: var(--text-lg);
  font-weight: var(--weight-semibold);
}

.concept-chevron {
  color: var(--text-tertiary);
  transition: transform var(--transition-fast);
  flex-shrink: 0;
}

.concept-section.open .concept-chevron {
  transform: rotate(180deg);
}

.concept-body {
  padding: 0 var(--space-6) var(--space-6);
}

.concept-content {
  font-size: var(--text-base);
  line-height: var(--leading-relaxed);
  color: var(--text-secondary);
}

.concept-content p {
  margin-bottom: var(--space-4);
}

.concept-content p:last-child {
  margin-bottom: 0;
}

.concept-content strong {
  color: var(--text-primary);
  font-weight: var(--weight-semibold);
}

.concept-content ul, .concept-content ol {
  margin: var(--space-3) 0;
  padding-left: var(--space-6);
}

.concept-content li {
  margin-bottom: var(--space-2);
}

/* ============================================
   CALLOUT BOXES
   ============================================ */
.callout {
  display: flex;
  gap: var(--space-3);
  padding: var(--space-4) var(--space-5);
  border-radius: var(--radius-lg);
  border-left: 4px solid;
}

.callout--key-insight {
  background: var(--color-info-bg);
  border-color: var(--color-info);
}

.callout--warning {
  background: var(--color-warning-bg);
  border-color: var(--color-warning);
}

.callout--example {
  background: var(--color-success-bg);
  border-color: var(--color-success);
}

.callout--tip {
  background: var(--color-info-bg);
  border-color: var(--color-teal);
}

.callout-icon {
  flex-shrink: 0;
  margin-top: 2px;
}

.callout--key-insight .callout-icon { color: var(--color-info); }
.callout--warning .callout-icon { color: var(--color-warning); }
.callout--example .callout-icon { color: var(--color-success); }
.callout--tip .callout-icon { color: var(--color-teal); }

.callout-title {
  font-weight: var(--weight-semibold);
  font-size: var(--text-sm);
  margin-bottom: var(--space-1);
}

.callout-text {
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  color: var(--text-secondary);
}

/* ============================================
   QUIZZES
   ============================================ */
.quiz-block {
  background: var(--bg-elevated);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
}

.quiz-header {
  margin-bottom: var(--space-4);
}

.quiz-badge {
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-pink);
  background: color-mix(in srgb, var(--color-pink) 10%, transparent);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
}

.quiz-question {
  font-size: var(--text-base);
  font-weight: var(--weight-medium);
  margin-bottom: var(--space-4);
  line-height: var(--leading-relaxed);
}

.quiz-hint-text {
  font-size: var(--text-sm);
  color: var(--text-tertiary);
  margin-bottom: var(--space-4);
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
  margin-bottom: var(--space-4);
}

.quiz-option {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  background: var(--bg-secondary);
  border: 2px solid var(--border-primary);
  border-radius: var(--radius-md);
  text-align: left;
  transition: all var(--transition-fast);
  cursor: pointer;
}

.quiz-option:hover:not(.correct):not(.incorrect) {
  border-color: var(--color-navy);
  background: color-mix(in srgb, var(--color-navy) 5%, transparent);
}

.quiz-option.selected {
  border-color: var(--color-navy);
  background: color-mix(in srgb, var(--color-navy) 8%, transparent);
}

.quiz-option.correct {
  border-color: var(--color-success);
  background: var(--color-success-bg);
}

.quiz-option.incorrect {
  border-color: var(--color-error);
  background: var(--color-error-bg);
}

.quiz-option-letter {
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-sm);
  background: var(--bg-tertiary);
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  color: var(--text-tertiary);
  flex-shrink: 0;
}

.quiz-option.selected .quiz-option-letter {
  background: var(--color-navy);
  color: white;
}

.quiz-option.correct .quiz-option-letter {
  background: var(--color-success);
  color: white;
}

.quiz-option.incorrect .quiz-option-letter {
  background: var(--color-error);
  color: white;
}

.quiz-option-text {
  flex: 1;
  font-size: var(--text-sm);
}

.quiz-actions {
  display: flex;
  gap: var(--space-3);
}

.quiz-check-btn {
  padding: var(--space-2) var(--space-5);
  background: var(--pink);
  color: white;
  border-radius: var(--r-full);
  font-weight: var(--weight-semibold);
  font-size: var(--text-sm);
  transition: all var(--transition-fast);
}

.quiz-check-btn:hover:not(:disabled) {
  background: var(--pink-dark);
}

.quiz-check-btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

.quiz-retry-btn {
  padding: var(--space-2) var(--space-5);
  background: var(--bg-tertiary);
  color: var(--text-secondary);
  border-radius: var(--radius-md);
  font-weight: var(--weight-medium);
  font-size: var(--text-sm);
  transition: all var(--transition-fast);
}

.quiz-retry-btn:hover {
  background: var(--border-primary);
}

.quiz-explanation {
  margin-top: var(--space-4);
  padding: var(--space-4);
  background: var(--color-success-bg);
  border-radius: var(--radius-md);
  border-left: 3px solid var(--color-success);
}

.quiz-explanation-content {
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  color: var(--text-secondary);
}

/* Drag and Match */
.drag-match-container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
  margin-bottom: var(--space-4);
}

@media (max-width: 600px) {
  .drag-match-container {
    grid-template-columns: 1fr;
  }
}

.drag-match-column {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

.drag-left-item, .drag-right-item {
  padding: var(--space-3) var(--space-4);
  background: var(--bg-secondary);
  border: 2px solid var(--border-primary);
  border-left: 4px solid var(--border-primary);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  cursor: pointer;
  transition: all var(--transition-fast);
  user-select: none;
}

.drag-left-item {
  cursor: grab;
}

.drag-left-item:active {
  cursor: grabbing;
}

.drag-left-item:hover, .drag-right-item:hover {
  border-color: var(--color-navy);
}

.drag-left-item.selecting {
  border-color: var(--color-navy);
  background: color-mix(in srgb, var(--color-navy) 8%, transparent);
  box-shadow: var(--shadow-sm);
}

.drag-left-item.paired, .drag-right-item.paired {
  background: color-mix(in srgb, var(--color-navy) 5%, transparent);
}

.drag-left-item.dragging {
  opacity: 0.5;
}

.drag-right-item.drag-over {
  border-color: var(--color-navy);
  background: color-mix(in srgb, var(--color-navy) 10%, transparent);
  box-shadow: var(--shadow-sm);
}

.drag-left-item.correct, .drag-right-item.correct {
  border-color: var(--color-success);
  background: var(--color-success-bg);
}

.drag-left-item.incorrect, .drag-right-item.incorrect {
  border-color: var(--color-error);
  background: var(--color-error-bg);
}

/* ============================================
   EXERCISES
   ============================================ */
.exercise-block {
  background: var(--bg-elevated);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
}

.exercise-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-3);
}

.exercise-header-left {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--text-primary);
}

.exercise-title {
  font-size: var(--text-base);
  font-weight: var(--weight-semibold);
}

.exercise-badge {
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--module-4-color);
  background: color-mix(in srgb, var(--module-4-color) 10%, transparent);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
}

.exercise-prompt {
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  color: var(--text-secondary);
  margin-bottom: var(--space-4);
}

.exercise-hints {
  margin-bottom: var(--space-4);
}

.exercise-hints-toggle {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  color: var(--color-navy);
  font-weight: var(--weight-medium);
}

[data-theme="dark"] .exercise-hints-toggle {
  color: var(--color-teal);
}

.exercise-hints-list {
  margin-top: var(--space-2);
  padding-left: var(--space-6);
  font-size: var(--text-sm);
  color: var(--text-secondary);
}

.exercise-hints-list li {
  margin-bottom: var(--space-1);
}

.exercise-textarea {
  width: 100%;
  padding: var(--space-4);
  background: var(--bg-secondary);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-md);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  resize: vertical;
  min-height: 160px;
  transition: border-color var(--transition-fast);
}

.exercise-textarea:focus {
  outline: none;
  border-color: var(--color-navy);
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--color-navy) 15%, transparent);
}

.exercise-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: var(--space-2);
}

.exercise-footer-left {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

.exercise-word-count, .exercise-saved-time {
  font-size: var(--text-xs);
  color: var(--text-tertiary);
}

.exercise-reset-btn {
  font-size: var(--text-xs);
  color: var(--text-tertiary);
  padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.exercise-reset-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text-secondary);
}

/* ============================================
   TAKEAWAYS
   ============================================ */
.takeaway {
  background: color-mix(in srgb, var(--color-teal) 6%, var(--bg-elevated));
  border: 1px solid color-mix(in srgb, var(--color-teal) 20%, var(--border-primary));
  border-radius: var(--radius-lg);
  padding: var(--space-5) var(--space-6);
}

.takeaway-header {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin-bottom: var(--space-3);
  color: var(--color-teal);
}

[data-theme="dark"] .takeaway-header {
  color: var(--color-teal-light);
}

.takeaway-title {
  font-size: var(--text-base);
  font-weight: var(--weight-semibold);
  color: var(--text-primary);
}

.takeaway-list {
  padding-left: var(--space-5);
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
  color: var(--text-secondary);
}

.takeaway-list li {
  margin-bottom: var(--space-2);
}

.takeaway-list li:last-child {
  margin-bottom: 0;
}

/* ============================================
   TOPIC NAVIGATION
   ============================================ */
.topic-complete-section {
  display: flex;
  justify-content: center;
  padding: var(--space-8) 0;
  border-top: 1px solid var(--border-primary);
  margin-top: var(--space-8);
}

.topic-complete-btn {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  background: transparent;
  border: 2px solid var(--pink);
  border-radius: var(--r-full);
  font-weight: var(--weight-semibold);
  font-size: var(--text-sm);
  color: var(--pink);
  transition: all var(--transition-fast);
}

.topic-complete-btn:hover {
  background: var(--pink);
  color: white;
}

.topic-complete-btn.completed {
  background: var(--pink);
  border-color: var(--pink);
  color: white;
}

.topic-nav {
  display: flex;
  justify-content: space-between;
  gap: var(--space-4);
  padding-top: var(--space-6);
}

.topic-nav-btn {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-4) var(--space-5);
  background: var(--bg-elevated);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-lg);
  color: var(--text-primary);
  transition: all var(--transition-fast);
  max-width: 45%;
}

.topic-nav-btn:hover {
  box-shadow: var(--shadow-sm);
  border-color: var(--border-secondary);
  color: var(--text-primary);
}

.topic-nav-label {
  display: block;
  font-size: var(--text-xs);
  color: var(--text-tertiary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.topic-nav-title {
  display: block;
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
}

.topic-nav-next {
  text-align: right;
  margin-left: auto;
}

/* ============================================
   DIAGRAMS
   ============================================ */
.diagram {
  margin: var(--space-5) 0;
  border-radius: var(--radius-lg);
  overflow: hidden;
}

/* Stack diagram */
.diagram-stack {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.stack-layer {
  padding: var(--space-4) var(--space-5);
  background: color-mix(in srgb, var(--layer-color) 10%, var(--bg-secondary));
  border-left: 4px solid var(--layer-color);
}

.stack-layer-label {
  font-size: var(--text-sm);
  font-weight: var(--weight-semibold);
  color: var(--text-primary);
  margin-bottom: var(--space-2);
}

.stack-layer-items {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.stack-item {
  font-size: var(--text-xs);
  padding: var(--space-1) var(--space-2);
  background: var(--bg-elevated);
  border-radius: var(--radius-sm);
  color: var(--text-secondary);
  border: 1px solid var(--border-primary);
}

/* Flow diagram */
.diagram-flow {
  padding: var(--space-5);
  background: var(--bg-secondary);
  overflow-x: auto;
}

.flow-nodes {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  min-width: min-content;
}

.flow-node {
  padding: var(--space-3) var(--space-4);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: var(--weight-medium);
  color: white;
  background: var(--node-color);
  white-space: nowrap;
  flex-shrink: 0;
}

.flow-node--start, .flow-node--end {
  border-radius: var(--radius-full);
}

.flow-node--decision {
  transform: rotate(0deg);
  border-radius: var(--radius-sm);
}

.flow-arrow {
  flex-shrink: 0;
}

/* Comparison diagram */
.diagram-comparison {
  padding: var(--space-4);
  background: var(--bg-secondary);
}

.comparison-columns {
  display: grid;
  grid-template-columns: repeat(var(--col-count), 1fr);
  gap: var(--space-3);
}

@media (max-width: 600px) {
  .comparison-columns {
    grid-template-columns: 1fr;
  }
}

.comparison-column {
  background: var(--bg-elevated);
  border-radius: var(--radius-md);
  border-top: 3px solid var(--col-color);
  overflow: hidden;
}

.comparison-column-header {
  padding: var(--space-3) var(--space-4);
  font-weight: var(--weight-semibold);
  font-size: var(--text-sm);
  color: var(--col-color);
}

.comparison-column-items {
  padding: 0 var(--space-4) var(--space-4);
  list-style: none;
}

.comparison-column-items li {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  padding: var(--space-2) 0;
  border-bottom: 1px solid var(--border-primary);
}

.comparison-column-items li:last-child {
  border-bottom: none;
}

/* Timeline diagram */
.diagram-timeline {
  padding: var(--space-5);
  background: var(--bg-secondary);
  overflow-x: auto;
}

.timeline-track {
  display: flex;
  gap: var(--space-6);
  position: relative;
  padding-top: var(--space-4);
  min-width: min-content;
}

.timeline-track::before {
  content: '';
  position: absolute;
  top: calc(var(--space-4) + 5px);
  left: 0;
  right: 0;
  height: 2px;
  background: var(--border-secondary);
}

.timeline-event {
  position: relative;
  flex-shrink: 0;
}

.timeline-dot {
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--border-secondary);
  border: 2px solid var(--bg-secondary);
  margin-bottom: var(--space-2);
}

.timeline-event.current .timeline-dot {
  background: var(--color-pink);
  box-shadow: 0 0 0 4px color-mix(in srgb, var(--color-pink) 20%, transparent);
}

.timeline-year {
  display: block;
  font-size: var(--text-xs);
  font-weight: var(--weight-bold);
  color: var(--text-primary);
}

.timeline-label {
  display: block;
  font-size: var(--text-xs);
  color: var(--text-secondary);
  max-width: 100px;
}

/* ============================================
   SEARCH OVERLAY
   ============================================ */
.search-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  backdrop-filter: blur(4px);
  z-index: 200;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  padding-top: 15vh;
}

.search-modal {
  width: 90%;
  max-width: 600px;
  background: var(--bg-elevated);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-xl);
  overflow: hidden;
  max-height: 60vh;
  display: flex;
  flex-direction: column;
}

.search-input-wrap {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-4) var(--space-5);
  border-bottom: 1px solid var(--border-primary);
}

.search-input-wrap svg {
  color: var(--text-tertiary);
  flex-shrink: 0;
}

.search-input-wrap input {
  flex: 1;
  border: none;
  background: none;
  outline: none;
  font-size: var(--text-base);
}

.search-input-wrap kbd {
  font-family: var(--font-sans);
  font-size: var(--text-xs);
  background: var(--bg-tertiary);
  padding: 2px 8px;
  border-radius: 4px;
  border: 1px solid var(--border-primary);
  color: var(--text-tertiary);
}

.search-results {
  overflow-y: auto;
  padding: var(--space-2);
}

.search-empty {
  padding: var(--space-8);
  text-align: center;
  color: var(--text-tertiary);
  font-size: var(--text-sm);
}

.search-group {
  margin-bottom: var(--space-2);
}

.search-group-header {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-3);
  font-size: var(--text-xs);
  text-decoration: none;
}

.search-group-module {
  font-weight: var(--weight-semibold);
}

.search-group-topic {
  color: var(--text-tertiary);
}

.search-result-item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--text-secondary);
  text-decoration: none;
  transition: background var(--transition-fast);
}

.search-result-item:hover {
  background: var(--bg-tertiary);
  color: var(--text-secondary);
}

.search-result-type {
  font-size: var(--text-xs);
  color: var(--text-tertiary);
  background: var(--bg-tertiary);
  padding: 1px 6px;
  border-radius: var(--radius-sm);
  flex-shrink: 0;
  margin-top: 2px;
}

.search-result-snippet {
  line-height: var(--leading-normal);
}

.search-result-snippet mark {
  background: color-mix(in srgb, var(--color-yellow) 30%, transparent);
  color: inherit;
  padding: 0 2px;
  border-radius: 2px;
}

/* ============================================
   FLASHCARD OVERLAY
   ============================================ */
.flashcard-overlay {
  position: fixed;
  inset: 0;
  background: var(--bg-primary);
  z-index: 200;
  overflow-y: auto;
}

.flashcard-container {
  max-width: 600px;
  margin: 0 auto;
  padding: var(--space-6);
}

.flashcard-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-6);
}

.flashcard-header h2 {
  font-size: var(--text-xl);
  font-weight: var(--weight-bold);
}

.flashcard-progress {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: var(--text-sm);
  color: var(--text-tertiary);
}

.flashcard-progress-bar {
  width: 100px;
  height: 4px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.flashcard-progress-fill {
  height: 100%;
  background: var(--color-navy);
  border-radius: var(--radius-full);
  transition: width var(--transition-slow);
}

.flashcard-close-btn {
  width: 40px;
  height: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-md);
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.flashcard-close-btn:hover {
  background: var(--bg-tertiary);
  color: var(--text-primary);
}

.flashcard-meta {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  margin-bottom: var(--space-4);
}

.flashcard-meta span:first-child {
  font-weight: var(--weight-semibold);
}

.flashcard-meta span:last-child {
  color: var(--text-tertiary);
}

.flashcard-card {
  perspective: 1000px;
  cursor: pointer;
  margin-bottom: var(--space-6);
  min-height: 250px;
}

.flashcard-card-inner {
  position: relative;
  width: 100%;
  min-height: 250px;
  transition: transform 0.5s ease;
  transform-style: preserve-3d;
}

.flashcard-card.flipped .flashcard-card-inner {
  transform: rotateY(180deg);
}

.flashcard-front, .flashcard-back {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--space-8);
  background: var(--bg-elevated);
  border: 1px solid var(--border-primary);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
}

.flashcard-front p, .flashcard-back p {
  font-size: var(--text-lg);
  text-align: center;
  line-height: var(--leading-relaxed);
}

.flashcard-back {
  transform: rotateY(180deg);
  background: var(--bg-secondary);
}

.flashcard-tap-hint {
  margin-top: var(--space-4);
  font-size: var(--text-xs);
  color: var(--text-tertiary);
}

.flashcard-rating {
  opacity: 0;
  transition: opacity var(--transition-base);
  text-align: center;
}

.flashcard-rating.visible {
  opacity: 1;
}

.flashcard-rating-label {
  font-size: var(--text-sm);
  color: var(--text-tertiary);
  margin-bottom: var(--space-3);
}

.flashcard-rating-btns {
  display: flex;
  gap: var(--space-2);
  justify-content: center;
}

.fc-rate-btn {
  padding: var(--space-2) var(--space-5);
  border-radius: var(--radius-md);
  font-weight: var(--weight-semibold);
  font-size: var(--text-sm);
  transition: all var(--transition-fast);
}

.fc-rate-again { background: var(--color-error-bg); color: var(--color-error); }
.fc-rate-hard { background: var(--color-warning-bg); color: var(--color-warning); }
.fc-rate-good { background: var(--color-info-bg); color: var(--color-info); }
.fc-rate-easy { background: var(--color-success-bg); color: var(--color-success); }

.fc-rate-btn:hover {
  filter: brightness(0.95);
  transform: translateY(-1px);
}

.flashcard-empty {
  text-align: center;
  padding: var(--space-12) 0;
}

.flashcard-empty svg {
  color: var(--color-success);
  margin-bottom: var(--space-4);
}

.flashcard-empty h3 {
  font-size: var(--text-xl);
  margin-bottom: var(--space-2);
}

.flashcard-empty p {
  color: var(--text-secondary);
  font-size: var(--text-sm);
}

.flashcard-loading {
  text-align: center;
  padding: var(--space-12);
  color: var(--text-tertiary);
}

/* ============================================
   EMPTY STATE
   ============================================ */
.empty-state {
  text-align: center;
  padding: var(--space-16) var(--space-6);
  color: var(--text-tertiary);
}

.empty-state p {
  font-size: var(--text-lg);
}

/* ============================================
   AI CHAT PANEL
   ============================================ */

/* Floating selection popup */
#selection-popup {
  position: fixed;
  z-index: 400;
  display: none;
  align-items: center;
  gap: 5px;
  padding: 7px 13px;
  background: var(--navy);
  color: #fff;
  border-radius: 8px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  box-shadow: 0 4px 16px rgba(0,0,0,0.22);
  user-select: none;
  pointer-events: all;
}

#selection-popup::after {
  content: '';
  position: absolute;
  bottom: -6px;
  left: 50%;
  transform: translateX(-50%);
  border: 7px solid transparent;
  border-bottom: none;
  border-top-color: var(--navy);
}

#selection-popup:hover {
  background: #0a2470;
}

/* Panel */
#chat-panel {
  position: fixed;
  top: var(--header-height);
  right: 0;
  bottom: 0;
  width: 380px;
  background: var(--bg-primary);
  border-left: 1px solid var(--border);
  box-shadow: -4px 0 32px rgba(0,0,0,0.07);
  transform: translateX(100%);
  transition: transform 0.28s cubic-bezier(0.4, 0, 0.2, 1);
  z-index: 150;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}

#chat-panel.open {
  transform: translateX(0);
}

/* Header */
.chat-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 var(--space-4);
  height: 52px;
  border-bottom: 1px solid var(--border);
  flex-shrink: 0;
}

.chat-header-title {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--text-primary);
}

.chat-header-title svg {
  color: var(--navy);
}

.chat-header-actions {
  display: flex;
  align-items: center;
  gap: 2px;
}

.chat-header-btn {
  width: 28px;
  height: 28px;
  border: none;
  background: transparent;
  cursor: pointer;
  border-radius: 6px;
  color: var(--text-tertiary);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.15s, color 0.15s;
}

.chat-header-btn:hover {
  background: var(--bg-secondary);
  color: var(--text-primary);
}

.chat-settings-btn.has-key {
  color: var(--teal);
}

/* Messages scrollable area */
.chat-messages {
  flex: 1;
  overflow-y: auto;
  padding: var(--space-4);
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

/* Welcome empty state */
.chat-welcome {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  gap: var(--space-3);
  padding: var(--space-10) var(--space-4);
  color: var(--text-tertiary);
  margin: auto 0;
}

.chat-welcome svg {
  opacity: 0.35;
}

.chat-welcome p {
  font-size: var(--text-sm);
  line-height: 1.65;
  max-width: 260px;
}

/* Context card */
.chat-context-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-left: 3px solid var(--navy);
  border-radius: 8px;
  padding: var(--space-3);
  flex-shrink: 0;
}

.chat-context-label {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--navy);
  margin-bottom: var(--space-2);
}

.chat-context-text {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.5;
  font-style: italic;
}

/* Message bubbles */
.chat-msg {
  max-width: 94%;
  font-size: var(--text-sm);
  line-height: 1.65;
}

.chat-msg--user {
  align-self: flex-end;
  background: var(--navy);
  color: #fff;
  padding: var(--space-2) var(--space-3);
  border-radius: 12px;
  border-bottom-right-radius: 3px;
}

.chat-msg--ai {
  align-self: flex-start;
  color: var(--text-primary);
}

.chat-msg--ai p {
  margin: 0 0 var(--space-2);
}

.chat-msg--ai p:last-child,
.chat-msg--ai ul:last-child,
.chat-msg--ai ol:last-child {
  margin-bottom: 0;
}

.chat-msg--ai ul,
.chat-msg--ai ol {
  margin: 0 0 var(--space-2);
  padding-left: var(--space-5);
}

.chat-msg--ai li {
  margin-bottom: 3px;
}

.chat-msg--ai strong {
  font-weight: 600;
  color: var(--text-primary);
}

.chat-inline-code {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  padding: 1px 5px;
  border-radius: 4px;
  color: var(--navy);
}

.chat-error {
  color: var(--pink);
}

/* Streaming cursor */
@keyframes blink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0; }
}

.chat-cursor {
  display: inline-block;
  width: 7px;
  height: 13px;
  background: var(--navy);
  border-radius: 1px;
  margin-left: 2px;
  vertical-align: text-bottom;
  animation: blink 0.9s step-end infinite;
}

/* API key prompt */
.chat-key-prompt {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: var(--space-4);
  flex-shrink: 0;
}

.chat-key-prompt-title {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: var(--space-2);
}

.chat-key-prompt p {
  font-size: 12px;
  color: var(--text-secondary);
  line-height: 1.5;
  margin-bottom: var(--space-3);
}

.chat-key-row {
  display: flex;
  gap: var(--space-2);
  margin-bottom: var(--space-2);
}

.chat-key-input {
  flex: 1;
  min-width: 0;
  padding: var(--space-2) var(--space-3);
  border: 1px solid var(--border);
  border-radius: 8px;
  font-size: 12px;
  font-family: var(--font-mono);
  background: var(--bg-primary);
  color: var(--text-primary);
  outline: none;
}

.chat-key-input:focus { border-color: var(--navy); }
.chat-key-input.error { border-color: var(--pink); }

.chat-key-save {
  padding: var(--space-2) var(--space-3);
  background: var(--navy);
  color: #fff;
  border: none;
  border-radius: 8px;
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  white-space: nowrap;
  flex-shrink: 0;
}

.chat-key-save:hover { background: #0a2470; }

.chat-key-link {
  font-size: 12px;
  color: var(--navy);
  text-decoration: none;
}

.chat-key-link:hover { text-decoration: underline; }

/* Footer input */
.chat-footer {
  border-top: 1px solid var(--border);
  padding: var(--space-3);
  flex-shrink: 0;
}

.chat-input-row {
  display: flex;
  gap: var(--space-2);
  align-items: flex-end;
}

.chat-input {
  flex: 1;
  padding: 8px 12px;
  border: 1px solid var(--border);
  border-radius: 10px;
  font-size: var(--text-sm);
  font-family: var(--font-sans);
  background: var(--bg-secondary);
  color: var(--text-primary);
  resize: none;
  outline: none;
  line-height: 1.5;
  max-height: 120px;
  overflow-y: auto;
  transition: border-color 0.15s, background 0.15s;
}

.chat-input:focus {
  border-color: var(--navy);
  background: var(--bg-primary);
}

.chat-input:disabled { opacity: 0.55; }

.chat-input::placeholder { color: var(--text-tertiary); }

.chat-send-btn {
  width: 36px;
  height: 36px;
  border-radius: 10px;
  border: none;
  background: var(--navy);
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  transition: background 0.15s, opacity 0.15s;
}

.chat-send-btn:hover:not(:disabled) { background: #0a2470; }
.chat-send-btn:disabled { opacity: 0.45; cursor: default; }

/* Mobile: panel slides up from bottom */
@media (max-width: 768px) {
  #chat-panel {
    width: 100%;
    top: auto;
    height: 72vh;
    transform: translateY(100%);
    border-left: none;
    border-top: 1px solid var(--border);
    box-shadow: 0 -4px 32px rgba(0,0,0,0.12);
  }

  #chat-panel.open {
    transform: translateY(0);
  }
}

/* Dark theme overrides */
[data-theme="dark"] .chat-inline-code {
  background: var(--bg-tertiary);
  color: var(--teal);
}

[data-theme="dark"] .chat-cursor {
  background: var(--teal);
}

/* ============================================
   MOBILE OPTIMISATION (max-width: 768px)
   ============================================ */
@media (max-width: 768px) {

  /* --- Dashboard --- */
  .dashboard {
    padding: var(--space-6) 0 var(--space-8);
    text-align: center;
  }

  .dashboard-hero {
    padding: var(--space-6) 0 var(--space-6);
  }

  .dashboard-title {
    font-size: var(--text-3xl);
  }

  .dashboard-subtitle {
    font-size: var(--text-base);
    margin-bottom: var(--space-6);
  }

  .dashboard-stats {
    gap: var(--space-5);
    flex-wrap: wrap;
    justify-content: center;
  }

  .dashboard-stat-value {
    font-size: var(--text-2xl);
  }

  .module-cards {
    gap: var(--space-3);
  }

  .module-card {
    padding: var(--space-5);
    border-radius: var(--r-lg);
  }

  /* --- Topic view --- */
  .topic-title {
    font-size: var(--text-2xl);
  }

  .topic-breadcrumb {
    overflow: hidden;
    flex-wrap: nowrap;
    white-space: nowrap;
  }

  .topic-breadcrumb > span:last-child {
    overflow: hidden;
    text-overflow: ellipsis;
    min-width: 0;
  }

  .concept-section.expandable .concept-header {
    padding: var(--space-4) var(--space-4);
  }

  .concept-section:not(.expandable) {
    padding: var(--space-4) var(--space-4);
  }

  .concept-body {
    padding: 0 var(--space-4) var(--space-4);
  }

  .concept-content ul,
  .concept-content ol {
    padding-left: var(--space-4);
  }

  /* --- Callouts --- */
  .callout {
    padding: var(--space-3) var(--space-4);
    flex-direction: row;
  }

  /* --- Key takeaways --- */
  .takeaway-section {
    padding: var(--space-4);
  }

  /* --- Diagrams: wrap in horizontal scroll --- */
  .diagram-flow,
  .diagram-stack,
  .diagram-comparison,
  .diagram-timeline {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
  }

  .flow-nodes {
    min-width: max-content;
  }

  /* --- Quiz --- */
  .quiz-block {
    padding: var(--space-4);
  }

  .quiz-options {
    gap: var(--space-2);
  }

  .quiz-option {
    padding: var(--space-3) var(--space-3);
    font-size: var(--text-sm);
  }

  .quiz-actions {
    flex-direction: column;
  }

  .quiz-check-btn,
  .quiz-retry-btn {
    width: 100%;
    justify-content: center;
    text-align: center;
  }

  .drag-match-container {
    grid-template-columns: 1fr;
  }

  /* --- Exercise --- */
  .exercise-block {
    padding: var(--space-4);
  }

  .exercise-header {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-2);
  }

  .exercise-footer {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-2);
  }

  .exercise-textarea {
    min-height: 140px;
    font-size: var(--text-sm);
  }

  /* --- Topic nav buttons --- */
  .topic-nav {
    flex-direction: column;
    gap: var(--space-3);
  }

  .topic-nav-btn {
    max-width: 100%;
    width: 100%;
    box-sizing: border-box;
  }

  /* --- Complete button --- */
  .topic-complete-wrap {
    padding: var(--space-6) 0;
  }

  .topic-complete-btn {
    width: 100%;
    justify-content: center;
  }

  /* --- Flashcard overlay --- */
  .flashcard-overlay {
    padding: var(--space-4);
  }

  .flashcard-modal {
    max-width: 100%;
    width: 100%;
    border-radius: var(--r-lg);
  }

  .flashcard-card {
    height: 220px;
  }

  .flashcard-actions {
    flex-wrap: wrap;
    gap: var(--space-2);
  }

  .flashcard-rate-btn {
    flex: 1;
    min-width: 0;
    justify-content: center;
  }

  /* --- Search modal --- */
  .search-modal {
    max-width: calc(100vw - var(--space-8));
    border-radius: var(--r-lg);
  }

  /* --- Header search: already hidden via base.css --- */

  /* --- Sidebar overlay backdrop on mobile --- */
  .sidebar-overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.4);
    z-index: 49;
  }

  .sidebar-overlay.visible {
    display: block;
  }
}

[data-theme="dark"] .chat-msg--user {
  background: #1a3080;
}

[data-theme="dark"] #selection-popup {
  background: #1a3080;
}

[data-theme="dark"] #selection-popup::after {
  border-top-color: #1a3080;
}

[data-theme="dark"] #selection-popup:hover {
  background: #243aa0;
}